1. Field of the Invention
The present invention relates to an optical modulator holder, an optical device, and a projector.
2. Description of Related Art
There is a known conventional projector having an optical modulating device which modulates light beams emitted from a light source in accordance with image information to form an optical image, and a projection optical device which projects the light beam modulated by the optical modulating device in an enlarged manner.
In such projectors, the optical modulating device generally adopts, for example, an active-matrix driven optical modulator in which electro-optic material such as liquid crystal is enclosed and sealed between a pair of boards. More specifically, the pair of boards included the optical modulator consist of a drive board which is provided on the light-irradiation side and has data lines, scanning lines, switching elements, pixel electrodes, and the like formed to apply a drive voltage to the liquid crystal, and an opposite board which is provided on the light-incident side and has a common electrode and a black mask formed thereon.
On the light-incident side and the light-irradiation side of the optical modulator, an incident-side polarization plate and an irradiation-side polarization plate are provided respectively. Each of these polarization plates allows light beam having a predetermined polarization axis to pass.
When light beam emitted from a light source is irradiated on the optical modulator, the temperature of the optical modulator easily rises due to absorption of light by the layer of liquid crystal, the data lines and scanning lines formed on the driving board, the black mask formed on the opposite board, etc. Of the light beam emitted from the light source and the light beam which has passed through the optical modulator, light beam that has no predetermined polarization axis is absorbed by the incident-side polarization plate and the irradiation-side polarization plate, causing these polarization plates to heat.
Therefore, for a projector which internally has this kind of optical element, a structure having a cooling device with use of a cooling fluid has been proposed in order to restrain the temperature rise of the optical element (e.g., Reference: Japanese Patent Application Laid-Open Publication No. Hei 1-159684.)
That is, the cooling device disclosed in the Reference has a cooling chamber which supports an optical modulator and a polarization plate on the light-source side kept separate from each other and is filled with the cooling fluid. This cooling chamber is connected to and communicates with a radiator and a fluid pump by tubes and the like through which the cooling fluid flows. Therefore, the internal cooling fluid circulates through a flow path from the cooling chamber to the radiator, the fluid pump and back to the cooling chamber through the tubes. According to this structure, heat generated at light beam transmission areas of the optical modulator and the incident-side polarization plate by light beam emitted from the light source is released directly to the cooling fluid.
In the cooling device disclosed in the Reference, however, light beam irradiated from the light source transmits the cooling fluid and may thereby cause a problem as follows.
For example, if air bubbles and dust are mixed in the cooling fluid and irradiated by the light beam, images of those bubbles and dust are reflected on an optical image formed by the optical modulator.
Alternatively, for example, if the cooling fluid is caused to have a temperature difference, the cooling fluid is also caused to have variance in the refraction index, which results in shimmering of the optical image formed by the optical modulator.
Also alternatively, for example, if the cooling fluid deteriorates due to the light beam irradiated from the light source, transmittance of light beam drops, which causes deterioration in illumination intensity or color reproducibility of the optical image formed by the optical modulator.
Demands have hence arisen for a structure capable of maintaining stably an optical image formed by an optical modulator and capable of efficiently cooling the optical modulator.